The invention relates to steering systems for boats, e.g., waterjet driven boats.
Waterjet boats are propelled by drawing a stream of water through a channel in the bottom of the boat and ejecting the stream out the back of the boat. A typical waterjet has two steering components: a nozzle and a reversing bucket. The nozzle is a tubular element near the rear of the propulsion stream ("the jet") that rotates from side to side. Rotating the nozzle deflects the exiting stream, imparting a side component to the propulsion vector, thereby turning the boat to port (left) or to starboard (right). A nozzle in a waterjet boat essentially serves the same purpose as a rudder in a propeller driven boat.
The reversing bucket allows an operator to slow or back up the boat. The bucket is a curved element located at the aftmost portion of the jet, just behind the nozzle. Ordinarily, the bucket is elevated above the jet, and has no effect on the operation of the boat. When the bucket is lowered over the jet, it blocks the jet and reverses its direction, causing the boat to move backwards. If the bucket is only partially lowered, it reverses some of the jet, thereby reducing the forward thrust, but does not reverse the direction of the boat's motion. If the bucket is lowered to reverse approximately half of the jet, then a balance point is achieved, and forward thrust of the boat is eliminated.
Some waterjet boats also have a third steering element, called a bowthruster, for side to side movement at low speed. The bowthruster is typically a tube that runs laterally across the boat near the bow, below the waterline. A reversible propeller in the middle of the tube can thrust the boat in either sideways direction.
Waterjet boats have a number of advantages over traditional propeller driven boats, including reduced noise and low draft. Waterjet boats, however, can be notoriously difficult to control, particularly at low speeds, e.g., when docking. In prior art waterjet boats, maintaining a heading and adjusting course, particularly at very low speed, requires considerable training, especially for operators accustomed to traditional propeller boats.
To facilitate steering of boats in the open sea, some boats include autopilots. The autopilot, when activated by an operator, maintains the boat's current course. Some propeller boats also include a detent structure to lock in a boat's course. In these boats, the steering wheel includes a notch or a groove, and the mechanism steered by the wheel includes a corresponding notch or groove. When the pilot returns the wheel to a neutral position, the corresponding notch and groove engage, holding the wheel in the neutral position. In certain boats, the autopilot automatically engages when the pilot returns the wheel to the neutral position and the corresponding notch and groove engage.